local check_backspace = function()
    local col = vim.fn.col "." - 1
    return col == 0 or vim.fn.getline("."):sub(col, col):match "%s"
end

---when inside a snippet, seeks to the nearest luasnip field if possible, and checks if it is jumpable
---@param dir number 1 for forward, -1 for backward; defaults to 1
---@return boolean true if a jumpable luasnip field is found while inside a snippet
local function jumpable(dir)
    local luasnip_ok, luasnip = pcall(require, "luasnip")
    if not luasnip_ok then
        vim.notify('luasnip not ok')
        return false
    end

    local win_get_cursor = vim.api.nvim_win_get_cursor
    local get_current_buf = vim.api.nvim_get_current_buf

    local function inside_snippet()
        -- for outdated versions of luasnip
        if not luasnip.session.current_nodes then
            return false
        end

        local node = luasnip.session.current_nodes[get_current_buf()]
        if not node then
            return false
        end

        local snip_begin_pos, snip_end_pos = node.parent.snippet.mark:pos_begin_end()
        local pos = win_get_cursor(0)
        pos[1] = pos[1] - 1 -- LuaSnip is 0-based not 1-based like nvim for rows
        return pos[1] >= snip_begin_pos[1] and pos[1] <= snip_end_pos[1]
    end

    ---sets the current buffer's luasnip to the one nearest the cursor
    ---@return boolean true if a node is found, false otherwise
    local function seek_luasnip_cursor_node()
        -- for outdated versions of luasnip
        if not luasnip.session.current_nodes then
            return false
        end

        local pos = win_get_cursor(0)
        pos[1] = pos[1] - 1
        local node = luasnip.session.current_nodes[get_current_buf()]
        if not node then
            return false
        end

        local snippet = node.parent.snippet
        local exit_node = snippet.insert_nodes[0]

        -- exit early if we're past the exit node
        if exit_node then
            local exit_pos_end = exit_node.mark:pos_end()
            if (pos[1] > exit_pos_end[1]) or (pos[1] == exit_pos_end[1] and pos[2] > exit_pos_end[2]) then
                snippet:remove_from_jumplist()
                luasnip.session.current_nodes[get_current_buf()] = nil

                return false
            end
        end

        node = snippet.inner_first:jump_into(1, true)
        while node ~= nil and node.next ~= nil and node ~= snippet do
            local n_next = node.next
            local next_pos = n_next and n_next.mark:pos_begin()
            local candidate = n_next ~= snippet and next_pos and (pos[1] < next_pos[1])
                or (pos[1] == next_pos[1] and pos[2] < next_pos[2])

            -- Past unmarked exit node, exit early
            if n_next == nil or n_next == snippet.next then
                snippet:remove_from_jumplist()
                luasnip.session.current_nodes[get_current_buf()] = nil
                return false
            end

            if candidate then
                luasnip.session.current_nodes[get_current_buf()] = node
                return true
            end

            local ok
            ok, node = pcall(node.jump_from, node, 1, true) -- no_move until last stop
            if not ok then
                snippet:remove_from_jumplist()
                luasnip.session.current_nodes[get_current_buf()] = nil
                return false
            end
        end

        -- No candidate, but have an exit node
        if exit_node then
            -- to jump to the exit node, seek to snippet
            luasnip.session.current_nodes[get_current_buf()] = snippet
            return true
        end

        -- No exit node, exit from snippet
        snippet:remove_from_jumplist()
        luasnip.session.current_nodes[get_current_buf()] = nil
        return false
    end

    if dir == -1 then
        return inside_snippet() and luasnip.jumpable(-1)
    else
        return inside_snippet() and seek_luasnip_cursor_node() and luasnip.jumpable()
    end
end

---checks if emmet_ls is available and active in the buffer
---@return boolean true if available, false otherwise
local is_emmet_active = function()
    local clients = vim.lsp.buf_get_clients()
    for _, client in pairs(clients) do
        if client.name == "emmet_ls" then
            return true
        end
    end
    return false
end

local status_cmp_ok, cmp = pcall(require, "cmp")
if not status_cmp_ok then
    return
end
local status_luasnip_ok, luasnip = pcall(require, "luasnip")
if not status_luasnip_ok then
    return
end

require("luasnip.loaders.from_vscode").lazy_load() -- load freindly-snippets
require("luasnip.loaders.from_vscode").load({ -- load custom snippets
    paths = {
        vim.fn.stdpath("config") .. "/snippets/"
    }
})

local kind_icons = {
    Class = " ",         Color = " ",    Constant = "ﲀ ",  Constructor = " ", Enum = "練",
    EnumMember = " ",    Event = " ",    Field = " ",     File = "",
    Folder = " ",        Function = " ", Interface = "ﰮ ", Keyword = " ",
    Method = " ",        Module = " ",   Operator = "",   Property = " ",
    Reference = " ",     Snippet = " ",  Struct = " ",    Text = " ",
    TypeParameter = " ", Unit = "塞",      Value = " ",     Variable = " ",
}
local source_names = {
    nvim_lsp = "(LSP)",  treesitter = "(TS)",       emoji = "(Emoji)",   path = "(Path)",
    calc = "(Calc)",     cmp_tabnine = "(Tabnine)", vsnip = "(Snippet)", luasnip = "(Snippet)",
    buffer = "(Buffer)", spell = "(Spell)",
}
local duplicates = {
    buffer = 1,
    path = 1,
    nvim_lsp = 0,
    luasnip = 1,
}

cmp.setup({
    confirm_opts = {
        behavior = cmp.ConfirmBehavior.Replace,
        select = false,
    },
    experimental = {
        ghost_text = true,
        native_menu = false,
    },
    snippet = {
        expand = function(args)
            require("luasnip").lsp_expand(args.body)
        end,
    },
    window = {
        completion = cmp.config.window.bordered(),
        documentation = cmp.config.window.bordered(),
    },
    completion = {
        keyword_length = 1, ---@usage The minimum length of a word to complete on.
    },
    mapping = cmp.mapping.preset.insert {
        ["<C-k>"] = cmp.mapping.select_prev_item(),
        ["<C-j>"] = cmp.mapping.select_next_item(),
        ["<C-d>"] = cmp.mapping.scroll_docs(-4),
        ["<C-f>"] = cmp.mapping.scroll_docs(4),
        -- TODO: potentially fix emmet nonsense
        ["<Tab>"] = cmp.mapping(function(fallback)
            if cmp.visible() then
                cmp.select_next_item()
            elseif luasnip.expandable() then
                luasnip.expand()
            elseif jumpable(1) then
                luasnip.jump(1)
            elseif check_backspace() then
                fallback()
            elseif is_emmet_active() then
                return vim.fn["cmp#complete"]()
            else
                fallback()
            end
        end, {
            "i",
            "s",
        }),
        ["<S-Tab>"] = cmp.mapping(function(fallback)
            if cmp.visible() then
                cmp.select_prev_item()
            elseif jumpable(-1) then
                luasnip.jump(-1)
            else
                fallback()
            end
        end, {
            "i",
            "s",
        }),

        ["<C-p>"] = cmp.mapping.complete(),
        ["<C-e>"] = cmp.mapping.abort(),
        ["<CR>"] = cmp.mapping(function(fallback)
            if cmp.visible() and cmp.confirm(cmp.setup.confirm_opts) then
                if jumpable(1) then
                    luasnip.jump(1)
                end
                return
            end
            if jumpable(1) then
                if not luasnip.jump(1) then
                    fallback()
                end
            else
                fallback()
            end
        end),
    },
    sorting = {
        comparators = {
            cmp.config.compare.offset,
            cmp.config.compare.exact,
            cmp.config.compare.score,
            require("cmp-under-comparator").under,
            cmp.config.compare.kind,
            cmp.config.compare.sort_text,
            cmp.config.compare.length,
            cmp.config.compare.order,
        },
    },
    sources = {
        { name = "luasnip" },
        { name = "nvim_lsp" },
        { name = "buffer" },
        { name = "path" },
        { name = "cmp_tabnine" },
        { name = "nvim_lua" },
        { name = "spell" },
        { name = "emoji" },
        { name = "treesitter" },
        { name = 'nvim_lsp_signature_help' },
        { name = "crates" },
        { name = "calc" },
    },
    formatting = {
        fields = { "kind", "abbr", "menu" },
        format = function(entry, vim_item)
            local max_width = 0
            if max_width ~= 0 and #vim_item.abbr > max_width then
                vim_item.abbr = string.sub(vim_item.abbr, 1, max_width - 1) .. "…"
            end

            vim_item.kind = kind_icons[vim_item.kind]
            vim_item.menu = source_names[entry.source.name]
            vim_item.dup  = duplicates[entry.source.name] or 0
            return vim_item
        end,
    },
})

-- Use buffer source for `/` (if you enabled `native_menu`, this won't work anymore).
cmp.setup.cmdline({'/', '?'}, {
    mapping = cmp.mapping.preset.cmdline(),
    sources = {
        { name = 'buffer' }
    }
})

-- Use cmdline & path source for ':' (if you enabled `native_menu`, this won't work anymore).
cmp.setup.cmdline(':', {
    mapping = cmp.mapping.preset.cmdline(),
    sources = cmp.config.sources({
        { name = 'cmdline' }
    }, {
        { name = 'path' }
    })
})
